EP0210190A1 - Controlled boron doping of silicon. - Google Patents
Controlled boron doping of silicon.Info
- Publication number
- EP0210190A1 EP0210190A1 EP86900515A EP86900515A EP0210190A1 EP 0210190 A1 EP0210190 A1 EP 0210190A1 EP 86900515 A EP86900515 A EP 86900515A EP 86900515 A EP86900515 A EP 86900515A EP 0210190 A1 EP0210190 A1 EP 0210190A1
- Authority
- EP
- European Patent Office
- Prior art keywords
- layer
- boron
- silicon
- polysilicon
- silicon body
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
Links
- 229910052796 boron Inorganic materials 0.000 title claims abstract description 82
- ZOXJGFHDIHLPTG-UHFFFAOYSA-N Boron Chemical compound [B] ZOXJGFHDIHLPTG-UHFFFAOYSA-N 0.000 title claims abstract description 81
- 229910052710 silicon Inorganic materials 0.000 title claims abstract description 60
- 239000010703 silicon Substances 0.000 title claims abstract description 60
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims abstract description 67
- 238000000034 method Methods 0.000 claims abstract description 62
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 claims abstract description 59
- 229910021420 polycrystalline silicon Inorganic materials 0.000 claims abstract description 55
- 229920005591 polysilicon Polymers 0.000 claims abstract description 54
- 235000012239 silicon dioxide Nutrition 0.000 claims abstract description 25
- 239000000377 silicon dioxide Substances 0.000 claims abstract description 25
- 239000003990 capacitor Substances 0.000 claims abstract description 20
- 238000003860 storage Methods 0.000 claims abstract description 6
- 238000010438 heat treatment Methods 0.000 claims description 18
- 238000000151 deposition Methods 0.000 claims description 9
- 230000001590 oxidative effect Effects 0.000 claims description 8
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 6
- 229910052581 Si3N4 Inorganic materials 0.000 claims description 5
- HQVNEWCFYHHQES-UHFFFAOYSA-N silicon nitride Chemical compound N12[Si]34N5[Si]62N3[Si]51N64 HQVNEWCFYHHQES-UHFFFAOYSA-N 0.000 claims description 5
- 230000000717 retained effect Effects 0.000 claims description 4
- 238000009792 diffusion process Methods 0.000 abstract description 18
- 229910052681 coesite Inorganic materials 0.000 abstract description 16
- 229910052906 cristobalite Inorganic materials 0.000 abstract description 16
- 229910052682 stishovite Inorganic materials 0.000 abstract description 16
- 229910052905 tridymite Inorganic materials 0.000 abstract description 16
- 238000005530 etching Methods 0.000 abstract description 7
- 230000008030 elimination Effects 0.000 abstract description 2
- 238000003379 elimination reaction Methods 0.000 abstract description 2
- 230000001105 regulatory effect Effects 0.000 abstract 2
- 238000009413 insulation Methods 0.000 abstract 1
- 239000002019 doping agent Substances 0.000 description 20
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 7
- 239000001301 oxygen Substances 0.000 description 7
- 229910052760 oxygen Inorganic materials 0.000 description 7
- 239000004065 semiconductor Substances 0.000 description 7
- 239000000758 substrate Substances 0.000 description 6
- 230000008021 deposition Effects 0.000 description 5
- 239000007943 implant Substances 0.000 description 5
- 238000005468 ion implantation Methods 0.000 description 5
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 4
- 238000010884 ion-beam technique Methods 0.000 description 4
- 238000002955 isolation Methods 0.000 description 4
- 230000003647 oxidation Effects 0.000 description 4
- 238000007254 oxidation reaction Methods 0.000 description 4
- VRDIULHPQTYCLN-UHFFFAOYSA-N Prothionamide Chemical compound CCCC1=CC(C(N)=S)=CC=N1 VRDIULHPQTYCLN-UHFFFAOYSA-N 0.000 description 3
- 229910052785 arsenic Inorganic materials 0.000 description 3
- RQNWIZPPADIBDY-UHFFFAOYSA-N arsenic atom Chemical compound [As] RQNWIZPPADIBDY-UHFFFAOYSA-N 0.000 description 3
- 238000005229 chemical vapour deposition Methods 0.000 description 3
- 239000007789 gas Substances 0.000 description 3
- 239000011521 glass Substances 0.000 description 3
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 2
- KRHYYFGTRYWZRS-UHFFFAOYSA-N Fluorane Chemical compound F KRHYYFGTRYWZRS-UHFFFAOYSA-N 0.000 description 2
- BOTDANWDWHJENH-UHFFFAOYSA-N Tetraethyl orthosilicate Chemical group CCO[Si](OCC)(OCC)OCC BOTDANWDWHJENH-UHFFFAOYSA-N 0.000 description 2
- 238000010420 art technique Methods 0.000 description 2
- ILAHWRKJUDSMFH-UHFFFAOYSA-N boron tribromide Chemical compound BrB(Br)Br ILAHWRKJUDSMFH-UHFFFAOYSA-N 0.000 description 2
- 230000005669 field effect Effects 0.000 description 2
- 150000002500 ions Chemical class 0.000 description 2
- 229910052757 nitrogen Inorganic materials 0.000 description 2
- DDFHBQSCUXNBSA-UHFFFAOYSA-N 5-(5-carboxythiophen-2-yl)thiophene-2-carboxylic acid Chemical compound S1C(C(=O)O)=CC=C1C1=CC=C(C(O)=O)S1 DDFHBQSCUXNBSA-UHFFFAOYSA-N 0.000 description 1
- 229910015845 BBr3 Inorganic materials 0.000 description 1
- -1 BF2 ions Chemical class 0.000 description 1
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 1
- 229910007991 Si-N Inorganic materials 0.000 description 1
- BLRPTPMANUNPDV-UHFFFAOYSA-N Silane Chemical compound [SiH4] BLRPTPMANUNPDV-UHFFFAOYSA-N 0.000 description 1
- 229910006294 Si—N Inorganic materials 0.000 description 1
- 230000004913 activation Effects 0.000 description 1
- 229910021417 amorphous silicon Inorganic materials 0.000 description 1
- 229910052786 argon Inorganic materials 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 239000012159 carrier gas Substances 0.000 description 1
- 238000003486 chemical etching Methods 0.000 description 1
- 230000000295 complement effect Effects 0.000 description 1
- 230000007423 decrease Effects 0.000 description 1
- 238000001312 dry etching Methods 0.000 description 1
- 230000009977 dual effect Effects 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 230000005684 electric field Effects 0.000 description 1
- 230000006870 function Effects 0.000 description 1
- 239000001257 hydrogen Substances 0.000 description 1
- 229910052739 hydrogen Inorganic materials 0.000 description 1
- 239000011261 inert gas Substances 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 230000015654 memory Effects 0.000 description 1
- 229910044991 metal oxide Inorganic materials 0.000 description 1
- 150000004706 metal oxides Chemical class 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 229910021421 monocrystalline silicon Inorganic materials 0.000 description 1
- 238000001020 plasma etching Methods 0.000 description 1
- 238000005204 segregation Methods 0.000 description 1
- 229910000077 silane Inorganic materials 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 238000007740 vapor deposition Methods 0.000 description 1
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
- H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
- H01L21/04—Manufacture or treatment of semiconductor devices or of parts thereof the devices having at least one potential-jump barrier or surface barrier, e.g. PN junction, depletion layer or carrier concentration layer
- H01L21/18—Manufacture or treatment of semiconductor devices or of parts thereof the devices having at least one potential-jump barrier or surface barrier, e.g. PN junction, depletion layer or carrier concentration layer the devices having semiconductor bodies comprising elements of Group IV of the Periodic System or AIIIBV compounds with or without impurities, e.g. doping materials
- H01L21/22—Diffusion of impurity materials, e.g. doping materials, electrode materials, into or out of a semiconductor body, or between semiconductor regions; Interactions between two or more impurities; Redistribution of impurities
- H01L21/225—Diffusion of impurity materials, e.g. doping materials, electrode materials, into or out of a semiconductor body, or between semiconductor regions; Interactions between two or more impurities; Redistribution of impurities using diffusion into or out of a solid from or into a solid phase, e.g. a doped oxide layer
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L29/00—Semiconductor devices adapted for rectifying, amplifying, oscillating or switching, or capacitors or resistors with at least one potential-jump barrier or surface barrier, e.g. PN junction depletion layer or carrier concentration layer; Details of semiconductor bodies or of electrodes thereof ; Multistep manufacturing processes therefor
- H01L29/66—Types of semiconductor device ; Multistep manufacturing processes therefor
- H01L29/86—Types of semiconductor device ; Multistep manufacturing processes therefor controllable only by variation of the electric current supplied, or only the electric potential applied, to one or more of the electrodes carrying the current to be rectified, amplified, oscillated or switched
- H01L29/92—Capacitors with potential-jump barrier or surface barrier
- H01L29/94—Metal-insulator-semiconductors, e.g. MOS
- H01L29/945—Trench capacitors
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
- H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
- H01L21/04—Manufacture or treatment of semiconductor devices or of parts thereof the devices having at least one potential-jump barrier or surface barrier, e.g. PN junction, depletion layer or carrier concentration layer
- H01L21/18—Manufacture or treatment of semiconductor devices or of parts thereof the devices having at least one potential-jump barrier or surface barrier, e.g. PN junction, depletion layer or carrier concentration layer the devices having semiconductor bodies comprising elements of Group IV of the Periodic System or AIIIBV compounds with or without impurities, e.g. doping materials
- H01L21/22—Diffusion of impurity materials, e.g. doping materials, electrode materials, into or out of a semiconductor body, or between semiconductor regions; Interactions between two or more impurities; Redistribution of impurities
- H01L21/225—Diffusion of impurity materials, e.g. doping materials, electrode materials, into or out of a semiconductor body, or between semiconductor regions; Interactions between two or more impurities; Redistribution of impurities using diffusion into or out of a solid from or into a solid phase, e.g. a doped oxide layer
- H01L21/2251—Diffusion into or out of group IV semiconductors
- H01L21/2254—Diffusion into or out of group IV semiconductors from or through or into an applied layer, e.g. photoresist, nitrides
- H01L21/2255—Diffusion into or out of group IV semiconductors from or through or into an applied layer, e.g. photoresist, nitrides the applied layer comprising oxides only, e.g. P2O5, PSG, H3BO3, doped oxides
- H01L21/2256—Diffusion into or out of group IV semiconductors from or through or into an applied layer, e.g. photoresist, nitrides the applied layer comprising oxides only, e.g. P2O5, PSG, H3BO3, doped oxides through the applied layer
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
- H01L21/70—Manufacture or treatment of devices consisting of a plurality of solid state components formed in or on a common substrate or of parts thereof; Manufacture of integrated circuit devices or of parts thereof
- H01L21/71—Manufacture of specific parts of devices defined in group H01L21/70
- H01L21/76—Making of isolation regions between components
- H01L21/762—Dielectric regions, e.g. EPIC dielectric isolation, LOCOS; Trench refilling techniques, SOI technology, use of channel stoppers
- H01L21/76224—Dielectric regions, e.g. EPIC dielectric isolation, LOCOS; Trench refilling techniques, SOI technology, use of channel stoppers using trench refilling with dielectric materials
- H01L21/76237—Dielectric regions, e.g. EPIC dielectric isolation, LOCOS; Trench refilling techniques, SOI technology, use of channel stoppers using trench refilling with dielectric materials introducing impurities in trench side or bottom walls, e.g. for forming channel stoppers or alter isolation behavior
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10S438/00—Semiconductor device manufacturing: process
- Y10S438/914—Doping
- Y10S438/923—Diffusion through a layer
Definitions
- the present invention relates to a technique for doping silicon with boron.
- One method for doping trench sidewalls is to fill the trench with a glass that contains the desired dopant, and then to diffuse the dopant into the trench sidewall by a heating step.
- a glass that contains the desired dopant is then frequently desirable to subsequently remove the glass dopant source, which in turn may create additional processing difficulties.
- the use of gas dopant source has also been considered.
- the solubility of the boron in silicon is so high that the doping is difficult to control. For example, a
- 5x10 1717 atoms/c 3 is typically desired for the p-type layer in trench capacitor sidewalls.
- the exposure of the sidewall to a boron-containing gas usually results in a doping level at the sidewall surface of about 1x1019 atoms/cm3. Even if a subsequent drive- in step is used to redistribute the boron deeper into the semiconductor, the doping concentration typically remains too high. Furthermore, the initial surface concentration is difficult to control.
- a dopant e.g., arsenic
- a dopant e.g., arsenic
- This technique utilizes the segregation effect, i.e., wherein the arsenic tends to be rejected from the moving silicon dioxide/silicon interface toward the silicon body.
- boron doping this technique has the disadvantage that boron increases the difficulty of subsequently removing the oxidized polysilicon layer from the silicon body after the diffusion step.
- a technique for doping with boron a silicon body typically, vertical surface in an integrated circuit.
- a layer of silicon dioxide is formed at least on the silicon feature to be doped.
- a layer of polysilicon is deposited on the silicon dioxide layer.
- the polysilicon is provided with the boron dopant therein, typically during, or after it is deposited.
- a subsequent heating step in an oxidizing ambient then causes the polysilicon to at least partially oxidize, and the boron to diffuse through the oxide layer into the silicon body.
- This heating step is optionally accomplished in an atomosphere that provides a source of water molecules, for example steam, to increase the diffusion rate of the boron through the oxide.
- An optional heating step in an inert ambient causes the boron to diffuse further into the silicon body, without transferring a substantial amount of additional boron from the polysilicon layer.
- the at least partially oxidized polysilicon layer and the silicon dioxide layer may be removed if desired, or retained.
- FIGS. 1-3 show in cross section a silicon semiconductor body having a trench, forming an Si0 2 layer, and depositing a polysilicon layer.
- FIG. 4 shows a preferred method of incorporating boron into the polysilicon layer by ion implantation, followed by redistribution.
- FIGS. 5-6 show transferring the boron into the silicon, followed by drive-in.
- FIGS. 7-10 show additional steps suitable for forming a trench capacitor.
- FIG. 11 shows forming the n+ layer prior to doping with boron to form the p-t- layer.
- FIG. 12 shows an isolation trench between n and p regions.
- a silicon semiconductor body 10 is shown.
- the body is typically a monocrystalline silicon substrate, or epitaxial layer formed thereon. It may alternately be a polycrystalline or amorphous silicon body.
- the silicon body 10 is lightly doped p-type material , suitable for forming n- channel field effect transistors therein.
- a trench 11 is formed in body 10, as by known etching techniques.
- One technique for forming the trench starts by forming a layer of silicon nitride on the silicon body, and then depositing a layer of SiO ⁇ . The trench opening is then lithographically defined, and the Si0 2 and
- Sl 3 N 4 la ⁇ ers serve as an etch mask for forming the trench (11).
- the Si0 2 layer (not shown) is then removed, leaving a layer of 5i 4 (13) on the silicon body (10).
- This layer is typically about 1000 angstroms thick for trench-forming purposes. This is sufficient to block the subsequent transfer of the boron into the silicon surfaces overlaid by layer 13.
- Other trench forming processes may substitute a SiO_ or other layer for the Si-N., or even omit such a layer. While the trench is shown rectangular for illustrative purposes, the etching process may result in a rounded or V-shaped bottom surface, rather than a flat surface, as shown. Furthermore, the sides of the trench may depart from the vertical to some degree. As used herein, sidewalls that are within plus or minus 20 degrees from being vertical to the major surface of the substrate are considered to be substantially vertical.
- a layer of silicon dioxide (20) is initially formed on the trench surface, including the bottom and sidewalls.
- the Si0 2 layer may also extend along the surface of the silicon body laterally from the trench, if desired, by prior removal of layer 13. If it is desired to prevent the subsequent transfer of boron into the horizontal surfaces surrounding the trench, the silicon nitride layer (13) can be retained.
- the Si0 2 layer serves two significant purposes in the present invention: firstly, it allows good control of the diffusion of the boron from the subsequently deposited polysilicon layer. This is because the diffusion rate of the boron is substantially less in the oxide than in either the silicon body or the polysilicon source layer. Further control of the diffusion is obtained through the choice of the ambient atmosphere during the heating steps described below.
- a steam ambient promotes diffusion of the boron through the silicon dioxide layer
- a dry ambient substantially reduces diffusion of the boron through the silicon dioxide layer.
- a difference in diffusion reates of over 10 may be obtained between a steam ambient as compared to a dry ambient.
- the "dry ambient” may be dry oxygen, or an inert gas. The latter also prevents further oxidation of the polysilicon layer 30, and prevents the possibility of oxidizing the underlying silicon body 10.
- An inert ambient even further reduces the diffusion rate of boron through the silicon dioxide layer as compared to a dry oxygen ambient. This degree of diffusion control is very advantageous for purposes noted below.
- the second purpose of the silicon dioxide layer (20) is to provide for etch selectivity when and if it is desired to remove the overlying polysilicon layer (30), since good etch selectivity is possible between polysilicon and silicon dioxide by known etching techniques. That is, the silicon dioxide can serve as an "etch stop". Furthermore, if it is desired to remove the silicon dioxide layer itself, that can also be accomplished by known etching techniques, with the silicon body then serving as the etch stop. For example, buffered HF, typically a mixture of ammonium fluoride and hydrofluoric acid, provides a very large etch selectivity when etching Si0 2 in the presence of Si".
- buffered HF typically a mixture of ammonium fluoride and hydrofluoric acid
- the SiO occasion layer 20 can be formed by heating the silicon body in an oxidizing ambient, such as 0 2 or steam, by proceudres known in the art.
- An oxidizing ambient such as 0 2 or steam
- a typical oxide thickness of 250 angstroms may be obtained by heating in a dry 0 2 ambient at 950° C for about 30 minutes.
- the use of plasma-assisted oxidation is also known, and allows for lower heating temperatures.
- the SiO ? layer may alternately be formed by deposition, as by the chemical vapor deposition of tetraethylorthosilicate (TEOS), or by other techniques known in the art.
- TEOS tetraethylorthosilicate
- a typical thickness of the silicon dioxide layer is in the range of from 100 to 500 angstroms (10 to 50 nanometers).
- the polysilicon layer 30 is deposited on the Si0 2 layer 20.
- the polysilicon layer serves as the source of the boron dopant, and hence is also referred to as the "source layer" herein.
- the polysilicon layer may be deposited by chemical vapor deposition (CVD) techniques known in the art. These techniques typically result in a conformal deposition of the polysilicon over the trench surfaces.
- CVD chemical vapor deposition
- a polysilicon thickness in the range of 2000 to 4000 angstroms is usually suitable.
- Boron dopant may be icorporated in the source layer 30 by l situ doping as the polysilicon is being deposited.
- the polysilicon layer may be exposed to a gas comprising boron after the deposition of layer 30 onto layer 20. This can form a boron glass on the surface of the polysilicon by a known chemical predeposition technique.
- FIG. 4 A presently preferred method of incorporating boron into the source layer is illustrated in FIG. 4, wherein an ion beam 40 implants a boron species, typically B or BF 2 ions from a BF_ source into the polysilicon layer 30.
- the species and implant energy are typically selected so that the boron is implanted into the polysilicon without exteding into oxide layer 20.
- An implant energy of about 30 KeV is typical.
- the boron will be implanted primarily into the horizontal surfaces as viewed, with relatively little being initially located in the vertical sidewalls, if the ion beam is directed vertically to the substrate surface, as shown. (The substrate may be tilted somewhat to include additional boron into the sidewalls.)
- the semiconductor body is heated to an elevated temperature, typically around 950 degrees centigrade for a period of 4 hours for a trench 4 micrometers deep or less. This serves to redistribute the boron more evenly throughout the polysilicon layer by rapid solid state diffusion, as indicated by the arrows 41, 42.
- the boron diffuses from the horizontal surfaces at both the top and bottom of the trench into the vertical sidewalls.
- the heating step that produces the redistribution is desirably accomplished in a dry ambient; that is, in an atmosphere that does not include a substantial amount of water molecules. This prevents a substantial amount of boron from migrating through the oxide if the temperature during redistribution is not excessive, being typically less than 1000° C.
- the ambient is also desirably inert for this step; a nitrogen or argon ambient is satisfactory.
- An inert ambient allows the redistribution to proceed in the polysilicon layer without oxidizing or otherwise reacting the polysilicon layer 30.
- the silicon body is exposed to an atmosphere comprising steam at an elevated temperature, in order to transfer the boron from the source layer 30 into the silicon body 10.
- an atmosphere comprising steam at an elevated temperature, in order to transfer the boron from the source layer 30 into the silicon body 10.
- One prior art technique for producing steam uses a carrier gas, typically nitrogen, to carry water vapor into a furnace.
- Another known technique pyrogenically combines oxygen and hydrogen to form H 2 0 ⁇ Ln situ.
- the atmosphere comprises at • le'ast a 10 percent partial pressure of steam at a total pressure of one atmosphere (760 mm of Hg) or more. Two processes occur durig the transfer step: the steam provides oxygen that oxidizes the polysilicon layer 30, beginning at the exposed surface.
- a SiO ⁇ /Si interface 51 thus moves inward from the exposed surface of layer 30 toward the silicon body 10, and hence toward Si0 2 layer 20.
- boron tends to segregate towards the oxide side of this interface. This tends to reduce the boron concentration in the remaining polysilicon as the "top” oxide grows.
- This oxidizing of source layer 30 may proceed until it is entirely converted to Si0 2 , or may be halted part-way through the process.
- the second process that occurs in the steam ambient is the diffusion of the boron from the source layer 30 through the Si0 2 layer 20 and into the silicon body 10. This is significantly facilitated by the presence of water molecules in the ambient, which increases the rate of boron diffusion through Sio 2 . I have determined that this second process allows sufficient boron to be transferred through oxide layer 20, even though the boron tends to be rejected toward the top oxide layer as it growns on the polysilicon.
- the result of this heating step also referred to as the "transfer” step herein, is relatively thin layer 50 of boron in the bottom and the vertical sidewalls of the trench; see FIG. 5.
- the inventive technique will be more fully illustrated by means of the following Examples.
- the transfer step may alternately be accomplished in a dry atmosphere if reduced diffusion rates of boron through the silicon dioxide are desired.
- a polysilicon layer (30) 4000 angstroms thick was implanted with 1X10 16 atoms/cm2 of boron. It was heated at 950° C for 1 hour in a dry oxygen ambient. This resulted in a transfer of boron into the underlying silicon body (10) to produce a surface doping level of
- Example Ii the use of a relatively thinner Si0 2 layer and a relatively longer heating time in dry oxygen as compared to the previous steam oxidation case (Example I) also resulted in a useful amount of boron transfer.
- the use of a steam ambient at 1 atmosphere pressure results in typically about 50 to 100 times more boron transfer than for a dry oxygen ambient.
- the transfer step is optionally followed by a dopant drive-in step that increases the depth of the boron doped region in silicon body 10; this expanded region is shown as 60 in FIG. 6. The concentration of boron in the expanded region is accordingly reduced.
- the drive-in step is accomplished in a dry atmosphere, to reduce or prevent further transfer of boron from the source layer.
- the atmosphere for drive-in is also desirably inert, to prevent further oxidation of the silicon body 10. It is apparent that Si0 2 layer 20 thus again provides for improved control of the doping process, due to the controllable nature of the boron transfer therethrough as a function of ambient atmosphere.
- the degree of boron diffusion can be estimated for a given time and temperature for the drive-in step, according to diffusion models known in the art.
- the oxide and polysilicon layer thicknesses, and implant dose provide additional degrees of control.
- Si_N 4 layer 13 has been retained (e.g., at the top of the trench), the transfer of the boron into the silicon body 10 is blocked.
- the drive-in tyically proceeds sufficiently to prevent overlap of the depletion regions of the adjacent trenches during operation.
- the top oxide protion (52) of the polysilicon source layer 30 and Si0 2 layer 20 may be removed by etching in buffered HF: see FIG. 7. If an unoxidized portion of the polysilicon source layer is present, it may be removed, followng removal of the top oxide, with KOH chemical etching, or by dry etching techniques known in the art. Following the removal of layers 30 and 20, a n+ doped region 80 may be formed, in order to serve as a plate of the capacitor and contact the source region of an n-channel access transistor (not shown), and to form a "high-C" capacitor cell; see FIG. 8.
- n+ region (81) may be formed prior to the formation of the trench, in order to connect region 80 to the source/drain region of the n-channel access transistor.
- the n+ regions (80, 81) may be produced by prior art techniques, such as that noted in U.S. Patent 4,472,212, .cited above.
- the n+ layers (80, 81) can be omitted.
- the capacitor is then electrically accessed by an inversion layer extending from the source of the access transistor around the trench, in lieu of the n+ layer.
- the layer 13 may optionally be removed.
- a dielectric for the capacitor may be formed by oxidizing the exposed silicn, including the doped sidewalls of the trench, to form Si0 2 layer 90; see FIG. 9.
- a silicon nitride layer can be deposited thereon to form a dual dielectric (not shown).
- Other steps can form a conductive region to serve as the inner plate of the capacitor, such as a doped polysilicon layer 100, shown in FIG. 10.
- the deposition of an oxide insulating layer (not sown) followed by an additional, relatively thick polysilicon layer, followed by anisotropic reactive ion etching, can be used to form a planarizing region 101 that fills the remaiing space in the trench.
- the sequench of the doping steps to form a capacitor may be varied.
- an n+ layer 110 may be initially formed in the silicon trench before applying the present technique. Then, the process steps noted above for FIGS. 2-6 may be used to obtain the boron (p+) doped region (not shown).
- the drive-in step can provide for the p+ region extending further into the silicon body 10 than the n+ region.
- the n+ doping level is typically greater than the p+ level, allowing a net n+ dopant type nearer the surface of the sidewall. This can result in the doped structure shown in FIG. 8, along with the presence of the Si0 2 layer (20) and the source layer (30) as shown in FIG. 3. Then, these latter two layers may remain on the silicon body, if desired.
- the layer 20 may serve as the dielectric of the capacitor.
- the remaing unoxided portion of polysilicon source layer 30 may be used as a plate of the capacitor.
- the present technique can be used to form the p+ region nearer the surface of the trench sidewall than the n+ region , as by the appropriate choice of drive-in conditions, or by elimination of the drive-in step.
- the present technique can also be used to dope the sidewall of an isolation trench between active devices.
- an isolation trench for complementary metal oxide silicon (CMOS) integrated circuits may utilize heavily doped n+ and p+ sidewalls to prevent inversion due to stray electric fields between n and p tub regions.
- CMOS complementary metal oxide silicon
- the present technique can be used to form the p+ region (120) on the sidewall contacting the p-tub (122). Futher ore, the walls of isoltin trenches between devices within the same p-tub may be doped by the present technique. In that case, both sidewalls of the trench may be p+ doped.
- the present technique may also be used to dope horizontal silicon surfaces, such as for sources and drains of p-channel field effect transistors.
- the controllability of boron transfer is also advantageous there.
- the present technique avoids direct ion implantation of the silicon body. Hence, there is substantially no ion damage to the silicon body by the present technique.
- the junction depths may be shallower than if direct ion implantation of the dopant into the silicon body is used.
- the boron doping concentration produced by the present technique is highest nearest the surface of the silicon body, and decreases with depth therein. This is frequently desirable to produce "lightly doped drain” structures or for other purposes, as it allows good electrical contact at the surface.” " (In contrast, direct ion implantation typically results in a maximum dopant concentration at some point below the surface.) Finally, the activation of the boron dopant may be accomplished during the transfer step of the present technique, avoiding a separate step.
Abstract
Technique de dopage d'un corps de silicium (10) avec du bore. La surface à doper est généralement la paroi latérale d'une tranchée, destinée à être utilisée comme condensateur de stockage ou pour l'isolation. En créant une couche de régulation de diffusion en bioxyde de silicium (20) et une couche source en polysilicium (30) qui incorpore le bore, il est possible d'obtenir un dopage au bore bien régulé dans une vaste plage de concentrations. La régulation du transfert de dopage peut être obtenue par le choix des environnements, soit secs soit en présence de vapeur. En outre, l'élimination des couches de bioxyde de silicium et de polysilicium après le processus de dopage est facilitée grâce à la sélectivité de gravure possible entre SiO2 et Si. Si on le désire, les couches peuvent rester sur le corps de silicium.Technique for doping a silicon body (10) with boron. The surface to be doped is generally the side wall of a trench, intended to be used as a storage capacitor or for insulation. By creating a diffusion regulating layer of silicon dioxide (20) and a source layer of polysilicon (30) which incorporates boron, it is possible to obtain a well regulated boron doping in a wide range of concentrations. The regulation of doping transfer can be obtained by the choice of environments, either dry or in the presence of vapor. Furthermore, the elimination of the layers of silicon dioxide and of polysilicon after the doping process is facilitated by virtue of the possible etching selectivity between SiO2 and Si. If desired, the layers can remain on the silicon body.
Description
Claims
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US06/694,806 US4604150A (en) | 1985-01-25 | 1985-01-25 | Controlled boron doping of silicon |
US694806 | 1985-01-25 |
Publications (2)
Publication Number | Publication Date |
---|---|
EP0210190A1 true EP0210190A1 (en) | 1987-02-04 |
EP0210190B1 EP0210190B1 (en) | 1991-07-24 |
Family
ID=24790354
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP86900515A Expired - Lifetime EP0210190B1 (en) | 1985-01-25 | 1985-12-16 | Controlled boron doping of silicon |
Country Status (8)
Country | Link |
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US (1) | US4604150A (en) |
EP (1) | EP0210190B1 (en) |
JP (1) | JPS62501530A (en) |
KR (2) | KR940008018B1 (en) |
CA (1) | CA1286573C (en) |
DE (1) | DE3583612D1 (en) |
ES (1) | ES8704553A1 (en) |
WO (1) | WO1986004454A1 (en) |
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IT1225625B (en) * | 1988-11-03 | 1990-11-22 | Sgs Thomson Microelectronics | PROCEDURE FOR THE IMPLEMENTATION OF INSULATION STRUCTURES BUILT IN THE SILICON SUBSTRATE FOR CMOS AND NMOS DEVICES. |
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DE59409300D1 (en) * | 1993-06-23 | 2000-05-31 | Siemens Ag | Process for the production of an isolation trench in a substrate for smart power technologies |
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JP3306258B2 (en) * | 1995-03-27 | 2002-07-24 | 三洋電機株式会社 | Method for manufacturing semiconductor device |
US5888876A (en) * | 1996-04-09 | 1999-03-30 | Kabushiki Kaisha Toshiba | Deep trench filling method using silicon film deposition and silicon migration |
TW304293B (en) * | 1996-11-18 | 1997-05-01 | United Microelectronics Corp | Manufacturing method for shallow trench isolation |
US6326293B1 (en) * | 1997-12-19 | 2001-12-04 | Texas Instruments Incorporated | Formation of recessed polysilicon plugs using chemical-mechanical-polishing (CMP) and selective oxidation |
US6107153A (en) * | 1998-01-26 | 2000-08-22 | Texas Instruments -Acer Incorporated | Method of forming a trench capacitor for a DRAM cell |
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CN115172518A (en) * | 2022-07-08 | 2022-10-11 | 酒泉正泰新能源科技有限公司 | Multiple oxidation diffusion method and preparation method of solar cell |
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- 1985-01-25 US US06/694,806 patent/US4604150A/en not_active Expired - Lifetime
- 1985-12-16 EP EP86900515A patent/EP0210190B1/en not_active Expired - Lifetime
- 1985-12-16 DE DE8686900515T patent/DE3583612D1/en not_active Expired - Fee Related
- 1985-12-16 WO PCT/US1985/002501 patent/WO1986004454A1/en active IP Right Grant
- 1985-12-16 KR KR1019860700659A patent/KR940008018B1/en active
- 1985-12-16 JP JP61500503A patent/JPS62501530A/en active Pending
-
1986
- 1986-01-21 CA CA000500041A patent/CA1286573C/en not_active Expired - Fee Related
- 1986-01-24 ES ES551229A patent/ES8704553A1/en not_active Expired
- 1986-09-24 KR KR1019860700659A patent/KR880700452A/en not_active IP Right Cessation
Non-Patent Citations (1)
Title |
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Also Published As
Publication number | Publication date |
---|---|
EP0210190B1 (en) | 1991-07-24 |
KR880700452A (en) | 1988-03-15 |
ES8704553A1 (en) | 1987-04-16 |
WO1986004454A1 (en) | 1986-07-31 |
US4604150A (en) | 1986-08-05 |
KR940008018B1 (en) | 1994-08-31 |
ES551229A0 (en) | 1987-04-16 |
CA1286573C (en) | 1991-07-23 |
JPS62501530A (en) | 1987-06-18 |
DE3583612D1 (en) | 1991-08-29 |
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